In metal welding such as arc welding, a welding wire fed to a welding torch is melted by arc heat to be consumed. Accordingly, the welding wire has to be continuously fed to the welding torch in response to a consumption amount in the welding torch.
This welding wire is drawn from a state of being wound around a spool or a state of being housed in a pack, to be fed to the welding torch. The drawn welding wire has a curling habit, and is bent or twisted. The welding wire thus having the curling habit is linearly straightened by a straightening device for straightening a curling habit, and thereafter is fed to the welding torch.
JP 2011-194443 A discloses a straightener for straightening bends or twists of a welding wire. The straightener described in JP 2011-194443 A includes three or more straightening units. In each of the straightening units, four or more rolls are arranged in zigzag so as to face with each other across a wire path. The three or more straightening units are arranged in series in the wire feeding direction. Bend in a plastic deformation region is applied to a wire by a first roll group on a wire entrance side, configured from first, second and third rolls of each straightening unit. A plastic deformation amount applied to the wire by a second roll group and subsequent groups configured from second, third, and fourth rolls is gradually lowered, and bend in an elastically deformation region is applied to the wire by a final roll group on an exit side. The three or more straightening units are arranged so that a roller axial direction has an angle difference distributed in a range of 90 degrees or more around a wire axis.